Wear-resistant, polycrystalline diamond compacts (“PDCs”) are utilized in a variety of mechanical applications. For example, PDCs are used in drilling tools (e.g., cutting elements, gage trimmers, etc.), machining equipment, bearing apparatuses, wire-drawing machinery, and in other mechanical apparatuses.
PDCs have found particular utility as superabrasive cutting elements in rotary drill bits, such as roller-cone drill bits and fixed-cutter drill bits. A PDC cutting element typically includes a superabrasive diamond layer commonly known as a diamond table. The diamond table is formed and bonded to a substrate using a high-pressure/high-temperature (“HPHT”) process. The PDC cutting element may be brazed directly into a preformed pocket, socket, or other receptacle formed in a bit body. The substrate may often be brazed or otherwise joined to an attachment member, such as a cylindrical backing. A rotary drill bit typically includes a number of PDC cutting elements affixed to the bit body. A stud carrying the PDC may also be used as a PDC cutting element when mounted to a bit body of a rotary drill bit by press-fitting, brazing, or otherwise securing the stud into a receptacle formed in the bit body.
Conventional PDCs are normally fabricated by placing a cemented carbide substrate into a container with a volume of diamond crystals positioned on a surface of the cemented-carbide substrate. A number of such containers may be loaded into a HPHT press. The substrate(s) and volume of diamond crystals are then processed at HPHT conditions in the presence of a metal-solvent catalyst that causes the diamond crystals to bond to one another to form a matrix of bonded diamond crystals defining a polycrystalline diamond (“PCD”) table. The metal-solvent catalyst is often made from cobalt, nickel, iron, or alloys thereof, and used for promoting intergrowth of the diamond crystals.
In one conventional approach, a constituent of the cemented carbide substrate, such as cobalt from a cobalt-cemented tungsten carbide substrate, liquefies and sweeps from a region adjacent to the volume of diamond crystals into interstitial regions between the diamond crystals during the HPHT process. The cobalt acts as a catalyst to promote intergrowth between the diamond crystals, which results in formation of bonded diamond crystals. Sometimes, a metal-solvent catalyst may be mixed with the diamond crystals prior to subjecting the diamond crystals and substrate to the HPHT process.
During the HPHT process, the metal-solvent catalyst dissolves carbon from the diamond crystals, carbon from portions of the diamond crystals that graphitize during the HPHT process, carbon swept-in with metal-solvent catalyst infiltrated from the cemented carbide substrate, or combinations thereof. The solubility of diamond in the metal-solvent catalyst is lower than that of the metastable graphite under diamond-stable HPHT conditions. Undersaturated graphite tends to dissolve into the metal-solvent catalyst and supersaturated diamond tends to deposit on and/or grow between existing diamond crystals to form a matrix of bonded-together diamond crystals with diamond-to-diamond bonding therebetween.